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Brake booster?

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NHinNC Avatar
NHinNC Larry C
Greensboro, NC, USA   USA
Brake pedal goes to the floor. The car had been sitting for 2 months or so.
Last summer, I noticed some reduction in the fluid level in the rear master cylinder reservoir.
There is no evidence of fluid anywhere. There was a little moisture in the drivers footwell end, I wiped it in November, and there is no more evidence there(but very little to no driving since then).
I would think, that if there was a master cylinder leak with a good booster, I would get moisture showing between the two.
So, my diagnosis is the booster.
Correct?

EDIT:
I forgot to point out that the rear reservoir is now dry.
The rear brakes were professionally rebuilt with new slaves, and I rebuilt the fronts, with new brake lines as well.



1976 TR6 Mimosa Yellow - not original
Purchased July 2015



Edited 1 time(s). Last edit at 2018-01-14 08:41 AM by NHinNC.

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poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
The rear compartment of the fluid reservoir holds the fluid for the front disc brakes. I don't know if that's much help in diagnosing the problem, though.

NHinNC Avatar
NHinNC Larry C
Greensboro, NC, USA   USA
Thinking more about it, I think that the rear seal on the master cylinder is bad. I also assume that the fluid is in the booster. But, this would only be true if there is a gasket between the master and the booster. Otherwise, I'd see fluid dripping there. I suppose I will have to start dismantling.



1976 TR6 Mimosa Yellow - not original
Purchased July 2015

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poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
I'd bet on the M/C too, Larry.
If it were the brake caliper, you'd see fluid around the rotor. If it were the rear cylinder,you'd see fluid dripping from the drum.
Plus if the hydraulic brake cylinders and calipers get rebuilt and the master cylinder, not..that would be the weak spot as far as withstanding the hydraulic pressure.
btw, there is no gasket between the M/C and servo. The only seal is the one internal to the M/C.

I have a suggestion..
If there is currently no leak at the location where the reservoir sits upon the M/C, don't replace those 2 seals. I had a devil of a time getting the new O-rings seals to seal.
Finally I had to relieve some of the plastic where the seals reside so that the seals had more exposure.



Edited 2 time(s). Last edit at 2018-01-14 11:27 AM by poolboy.

NHinNC Avatar
NHinNC Larry C
Greensboro, NC, USA   USA
I agree about the leaks at the calipers and wheel cylinders. The fluid had to go somewhere. With no gasket between the MC and servo, I'd expect to see leaking at the front of the servo, if it is the rear MC seal. I'm on my way out to the cool garage. I will jack up the car and check the rear lines for a leak somewhere, and then, if finding nothing, pull off the MC.



1976 TR6 Mimosa Yellow - not original
Purchased July 2015

poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
If you don't find it elsewhere, the fluid probably drained into the servo.
I don't know if it's possible but sometimes I wonder if the intake manifold sucks some of it out of the servo.



Edited 1 time(s). Last edit at 2018-01-15 10:37 AM by poolboy.

NHinNC Avatar
NHinNC Larry C
Greensboro, NC, USA   USA
In times of high vacuum, perhaps is does get sucked into the manifold. When I pulled off the vacuum line, I put the end into a dry can, and after a day, there was no drippage.

In my case, there was probably over a pint of fluid in the servo. So, no more mystery as to where the fluid went.
I am going to try to rehab the MC. I've never done one before, but having been laid off, money is crucial. Also, I just replaced the clutch MC, and while under the dash, I noticed a drop at the clutch pedal. So, damn near ever part i get for this car sucks. I gave up on TRF a while back, but this clutch MC was a Moss. Many things seem to be a piece of junk.
My new rear seal on the gearbox leaks.
The new orings on the shift selectors leak.
The new ignition switch was wrong.
The new glovebox lock does not work.
The new high beam switch works intermittently.
The new front upper arm bushings were incredibly sloppy.
The trunion thru bolts would not fit through the sleeves.
I ordered the specific type of carb float needles you claim work better, and I received the others.



1976 TR6 Mimosa Yellow - not original
Purchased July 2015

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NHinNC Avatar
NHinNC Larry C
Greensboro, NC, USA   USA
So, I drained the booster. I got at least 10 ounces of brake fluid. I'd like to clean out all of the fluid, as I am afraid it will degrade the diaphragm. I was thinking of spraying some Simple Green in the vacuum hole, add water and drain. perhaps I need to spray some WD40 after?
1) Anybody else clean their booster out?

I got a new grommet for the vacuum line at Autozone in one of those "Help" packages. The dust cover towards the pedal is fine, but the filter was in small soaked pieces.
2) Does anybody know what material the filter is?

I am wirebrushing the booster down, and will paint it.
3) I would think a regular gloss black?

I ordered a MC rebuild kit from Moss. Fingers crossed that it fits properly.

4) This *might* be a good time to switch to Dot 5. I can undo at the PDV and drain those lines, undo the bleeders. I think there may be fittings to undo in the back to drain also. Would this be sufficient, or would I have to push a bunch of Dot 5 through the lines to flush out all the Dot3?



1976 TR6 Mimosa Yellow - not original
Purchased July 2015

Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
Larry, I presume you've looked at the Buckeye Triumphs tech article about the brake booster rebuild. Excellent information. This may answer your questions.
I took my booster apart 20 years ago and it's still working fine but this spring I'm going to do it again along with the master.

http://www.buckeyetriumphs.org/technical/Brakes/Servo/Servo.htm

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NHinNC Avatar
NHinNC Larry C
Greensboro, NC, USA   USA
I do not want to tear the booster apart, because the diaphragm is mad of unobtainium. Otherwise, I sure would.



1976 TR6 Mimosa Yellow - not original
Purchased July 2015

DerekM Avatar
DerekM Silver Member Derek McAllister
Toronto, ON, Canada   CAN
I used a piece of car washing sponge (the big peanut shaped ones seem to have the right "texture" for the job) cut to fit to replace the NLA filter in my booster. I wire brushed the rust off and rattle canned it gloss black. I also replaced the fluid with dot 5 doing as you described. I drove last summer and had no issues, though I did bleed the 4 corners a fair amount until I got good colour fluid and no bubbles.



Derek McAllister
Toronto, Ontario
1974 TR6 Sapphire Blue/Shadow Blue

Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
I recently purchased the RF "minor" repair kit for the booster. It doesn't included the filter. So I'll make my own but I'm going to use the foam from a Briggs&Straton air filter. It's oil and fuel resistant so stands a slightly better chance of surviving brake fluids. Cut a slug out using a foam hole cutter.

ed.h Ed Hollingsworth
Omaha, NE, USA   USA
The filter in the pic was made from actual filter material that looks almost identical to the remnant of the original filter on the right.

Ed


Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
Nice Ed!!

Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
Larry, if you still wish to do a full rebuild including the main diaphragm, Apple Hydraulics has a full rebuild kit that includes the main diaphragm and all the little parts including the foam seal-$45. They will also rebuild your unit or sell you one outright.
I've used them to put a brass sleeve in my master cylinder. Both my TR250 and my GT6 have the brass sleeves.

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